In recent past, scarcity of fresh water has turned out to be a global issue, which may be due to excessive usage of the fresh water by the population or contamination of the clean water due to industry effluents, oil and gas rigs and the like. For conserving the fresh water, the existing technologies are capitalized for extracting potable water from saline water such as, but not limited to, seawater, waste water, contaminated water and the like.
The existing techniques for potable water extraction may be broadly categorized as distillation (or thermal desalination process) and membrane separation processes. The most efficient and most utilized of these techniques are multistage flash distillation (MSF), multiple effect evaporation (MEE), mechanical vapor recompression (MVR) and reverse osmosis (RO). However, costs i.e. energy costs and the capital cost are a major driving factor for all of these processes, which makes it inaccessible. Additionally, for an MSF plant, co-generated steam from an electric power generation facility is required as an energy input for heating the saline water to 110° C., which makes this process cumbersome and energy inefficient. Moreover, for an RO plant, the mechanical power for driving the saline water through an array of thousands of RO tubes in an RO desalination plant requires a tremendous amount of energy, which is undesirable. Further, in the desalination plant, issues of seawater pre-treatment by filtration, bio-fouling, scaling of mineral salts, corrosion of metallic parts, components, and valves by the chloride ions translate into premature failure of the components of the plant. This factor inherently requires frequent replacement of the components in the plant, rendering the maintenance of the plant to be tedious and cumbersome, which is undesirable.
Furthermore, a vacuum environment is indispensable for all the thermal desalination technologies. Either a steam ejector or a turbo compressor is typically employed to drive a unidirectional mass flow of water molecules to the condenser. The evaporation rate of liquid water from a falling film or water droplets from a spray nozzle inside an evaporator can only be optimized under a good vacuum. Boiling of saline water under a reduced pressure is the rule of thumb. Consequently, additional Roots and oil-free screw vacuum pumps should be installed to pump out non-condensable gases (air molecules) which are released continuously from saline water under reduced pressure, which is uneconomical.
Therefore, there is a need for techniques which can overcome one or more limitations stated above in addition to providing other technical advantages.